Traditional propulsion systems for catalyst-activated propellants pass a monopropellant through a fine-mesh screen or other fixed element coated with a catalyst that initiates an exothermic reaction that disassociates the propellant into one or more high temperature products that are expelled through a nozzle. An example engine may use hydrazine as the monopropellant and iridium as the catalyst, wherein the decomposition produces a 1000° C. gas that is a mixture of nitrogen, hydrogen, and ammonia.
Arcjet engines create an electric discharge, or “arc,” in the flow of propellant which accelerates the propellant at the expense of the power and weight of the equipment that creates the arc.